At present, 3rd Generation Partnership Project (3GPP) has put forward MBMS which can realize data transmission from a data source to multiple targets.
In Long Term Evolution (LTE), the MBMS service can be sent in a multicast mode, this sending mode is called a Multicast/Broadcast over Single Frequency Network (MBSFN) sending mode and the MBMS service sent in the multicast mode is called an MBSFN service. The characteristics of the MBMS multi-cell transmission comprise: 1) synchronous transmission in an MBSFN area; 2) supporting the combination of multi-cell MBMS transmission; 3) mapping a Multicast Traffic Channel (MTCH) and a Multicast Control Channel (MCCH) to a Multicast Channel (MCH) transmission channel in a point-To-multipoint (p-T-m) mode; 4) maintaining the MBSFN synchronous area, MBSFN area, MBSFN transmission, advertisements and reserved cells in a semi-static configuration by operation. User Equipment (UE) of a multiple cells can receive many pieces of MBMS data with same content and perform an SFN combination to increase the gain of a received signal. Multiple cells, which send a same MBMS service through the MBSFN mode by using same physical resources, form an MBSFN area. In an LTE networking, an MBSFN area has multiple MBSFN services, and all the MBSFN services in one MBSFN area are called an MBSFN service group. Each cell in an MBSFN area is configured with a completely identical MBSFN service group. The MTCH and MCCH of multiple MBSFN services with the same MBSFN area can be multiplexed to an MCH. The MCCH and multiple MTCHs (namely multiple logical channels) of the same MBSFN area can be mapped to the same transmission channel MCH.
As shown in FIG. 1, in order to increase the transmission efficiency of the MTCHs, the multiple MTCHs carried on an MCH can adopt a dynamic scheduling method, and two or more MTCHs are multiplexed to one MBSFN sub-frame and take up part of the resources of the sub-frame. In the prior art, MSAP occasion is used for indicating all multicast resources contained in the MCH corresponding to one MSAP during a dynamic scheduling period. In an MSAP occasion, multiple MTCHs and dynamic scheduling information can be sent, as well as the MCCH. The dynamic scheduling information can be carried in the control part of the Media Access Control (MAC) or in an independent logical channel, namely a Multicast Scheduling Channel (MSCH). Generally, the length of an MSAP occasion is 320 ms, and similarly, a dynamic scheduling period (a scheduling period for short) is 320 ms in general. The scheduling period also may be 2n×320 ms (n=−3, −2, −1, 0, 1, 2, 3, 4 . . . N), correspondingly, the length of MSAP occasion is 40 ms, 80 ms, 160 ms, 320 ms, 640 ms, 1280 ms and etc. A time length of an MSAP occasion is a scheduling period, also called a dynamic scheduling period. One or more MBSFN sub-frames in one or more MBSFN frames are allocated in an MCH by MSAP, wherein the sub-frames sent in the multicast mode are called MBSFN sub-frames and the frames including the MBSFN sub-frames are called MBSFN frames.
Each MSAP occasion configured in an MCH carries dynamic scheduling information and mapping information of MTCHs to auxiliary MSAP sub-frames. The mapping information can be determined by the MBSFN sub-frame number index relationship in a scheduling period. According to the scheduling information, UE learns the MBSFN sub-frame which each of the MTCHs locates, acquires the required MTCH and neglects the unnecessary MBSFN sub-frames to increase the MBMS service receiving efficiency of the UE and reduce power consumption.
Specifically, the numbers of the MBSFN sub-frames can be determined by the following way: arranging all the MBSFN sub-frames allocated in a scheduling period of the MCH in order, and numbering them. For example, the total number of the MBSFN sub-frames allocated in a period of the MCH channel is 100, the numbers of the sub-frames ranges from 0 to 99, or from 1 to 100.
In the current LTE technology, multiple logical channels multiplex an MCH channel by the following way that: a sub-frame corresponds to a Transmission Time Interval (TTI); one or more transmission data blocks can be sent in a TTI; each transmission data block corresponds to a MAC Protocol Data Unit (PDU). A MAC PDU can contain multiple MAC Service Data Units (SDU); each MAC SDU can be from different logical channels (including MTCH, MCCH, MSCH etc.).
For dynamical multiplexing of the MBMS services, an MTCH or the data of an MBMS service is sent continuously in a scheduling period, which means that the data of a service continuously takes up the MBSFN sub-frame resources of the MCH channel, until all the service data of the service required to be sent in the scheduling period are sent. The data from different services can be sent in a same MBSFN sub-frame, which means that the service data from different MBMS services can be concatenated and sent in the same MAC PDU.
A synchronous protocol processing (SYNC) method is disclosed in relevant technologies, which comprises:
step S102: an upper-layer network element sends an MBMS service data packet to all lower-layer network elements; the service data packet carries service data, time stamp information, data packet serial number information, information of accumulated service data length and etc; the upper-layer network element marks the same time stamp information for one or more continuous service data packets; the data packets marked with the same time stamp form a data burst, or are called a synchronization sequence;
currently, the time stamp information of each data packet can be set by the following two ways: (1) containing the reference time information indicating when the synchronization sequence starts to be sent on a radio interface in each of the data packets contained in the synchronization sequence; (2) containing the reference time information indicating when one synchronization sequence starts to be sent on a radio interface in each of the data packets contained in the synchronization sequence;
step S104: for the service data carried by the service data packets contained in the same synchronization sequence, the lower-layer network element begins to send the service data packets successively via the radio interface at the time corresponding to the time stamp; since the information sent by the upper-layer network element to the lower-layer network element is completely consistent, all the lower-layer network elements can perform the same treatment to realize synchronous transmission of the MBMS services among cells of the lower-layer network elements;
step 106: the lower-layer network element allocate radio interface resources for one or more MBMS services at the radio interface; the resources can be dedicated only to an MBMS or shared by multiple MBMS services through time-division multiplexing; for example, in the LTE system, the MBMS services share the resources of an MCH channel in a dynamic multiplexing manner, or in the UMTS system, the multiple MBMS services share the resources of the same SCCPCH channel in an MBSFN manner.
Since the aforementioned MBMS service channel resources are configured in a static or semi-static manner, which means that, during a certain time period, the resources will not be adjusted according to the amount of the service data required to be sent during a scheduling period, thus during a certain time period or a scheduling period, the data amount of an MBMS service or multiple multiplexed MBMS services surpasses the transmission ability of the transmission channel in a certain time period. Under such situation, redundant data will be discarded by the lower-layer network element. If multiple services are multiplexed to the same channel, the lower-layer network element will determine data of which service has to be discarded according to the priorities of the services. This is called data overflow. For example, as shown in FIG. 1, service S1 and service S2 share the same channel, time period 1 and time period 2 in FIG. 1 can be two scheduling periods. According to the SYNC protocol, there is service data of service data S1 to be sent in both of the time period 1 and time period 2. In the time period 1, because the service data amount of S1 and S2 surpasses the maximum transmission ability of the channel resources corresponding to the time period 1, thus part of the service data of S2 cannot be sent.
As mentioned above, due to the dynamical property of the MBMS service, the flow of the service data changes greatly in different time periods, which means that there may be a great difference among the service data required to be sent in different scheduling periods, especially under the situation that one service use one channel or multiple services multiplex a channel while the amount of service is relatively small. Furthermore, resource configuration cannot be increased unlimitedly to meet the requirement of the changes in the service flow. Therefore, the current service data scheduling method may result in loss of service data, which further reduce the service quality.